12. Stacks (LIFO) and Queues (FIFO)

These are abstract data types that restrict how data can be added or removed, making them crucial for certain algorithms.

Stacks (LIFO - Last-In, First-Out)

Think of a stack of plates. The last plate placed on top is the first one removed.

• Operations:
  • Push: Adds an item to the top (O(1)).
  • Pop: Removes the top item (O(1)).
• Use Cases: Function call management (recursion), undo/redo functionality, expression evaluation.

Queues (FIFO - First-In, First-Out)

Think of people waiting in line. The first person in line is the first one served.

• Operations:
  • Enqueue: Adds an item to the rear (O(1)).
  • Dequeue: Removes the front item (O(1)).
• Use Cases: Print job scheduling, operating system task management, Breadth-First Search (Graph Algorithms).